How to Calculate Grout
Three things drive how much grout you use: tile size, joint width and joint depth. Rule of thumb – the smaller the tile and the wider or deeper the joint, the more grout it swallows. The maths behind it works out the joint volume per square metre and multiplies it by the density. For a cement grout that density sits at roughly 1600 kg/m³.
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How to calculate grout
- Set tile size, joint width and joint depth.
- Work out joint volume per m² (see formula).
- Multiply by density (~1600 kg/m³) and area = kg.
- Divide by bag size and round up = bags.
Formula: kg/m² = ((A+B) ÷ (A×B)) × joint width × joint depth × density (A, B = tile dimensions)
Example: tile 60 × 30 cm, joint 3 mm wide, 8 mm deep, 20 m² → about 3.8 kg, i.e. 1 bag (25 kg).
Practical tips
- Large formats use less grout; small mosaics much more.
- Joint depth usually equals the tile thickness.
- Check the manufacturer's data – density and yield vary by product.
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Download on the App StoreCommon questions
How much grout per m²?
Depending on tile and joint, usually 0.3–1.5 kg/m²; more for small tiles, less for large formats.